Cellularity in breast carcinoma.

Tumor cellularities were observed in 23 consecutive cases of infiltrating ductal carcinoma of the breast and correlated with other morphometric, pathologic, and clinical features. The cellularity mean index (CMI), defined as the percentage of tumor volume occupied by invasive tumors cells, was found to correlate with lymph node involvement by tumor (P = 0.03) and the number of mitotic figures per ten high-power fields (P = 0.0002). The CMI also correlated with mitotic activity (P = 0.01) when the latter was expressed as the percentage of tumor cells actively in mitosis, thus correcting for differences in cellularity between individual tumors. The relationship between cellularity and mitotic activity is discussed.